We propose to study two aspects of gene expression, one related to regulation of initial transcription of DNA and the other related to selective post-transcriptional processess. The first is a study of differential gene expression in various rat tissues and tumor lines, with particular emphasis on the transcriptional diversity in brain. Others have shown that in the mouse, rabbit and human 3 minus 5, more unique sequence DNA is transcribed into RNA in the brain than in liver, kidney or spleen. In the case of the human brain, if the RNA encoded protein, this would be enough information to specify 10 to the minus 5th power minus 10 to the minus 6th power different 30,000 M.W. proteins. We propose to 1) determine if this high RNA sequence complexity in rat brain is found in cytoplasmic as well as nuclear RNA and 2) determine if this high transcriptional diversity is found in neural cells or results from the composite of many different individual cell- specific RNAs. For this, we will compare the transcriptional diversity of whole brain and its different lobes with that of clonal cell lines derived from independently arising, nitrosoethylurea-induced neurotumors, as well as separated neutron and glia populations. Our long range goal is to establish a possible correlation between the high RNA diversity in brain with the diversity in proteins necessary for the specificity of neural connections. This study in transcription complements the work in our laboratory on the plasma membrane proteins of neuro-cells and their tumors.